Conventionally, an apparatus is known, which overlays a coordinate input apparatus capable of inputting coordinates on the display window of a display such as a CRT display, liquid crystal display (LC), or projector, and displays a handwriting based on pointing or writing performed by an operator on the display, thereby realizing a relationship like the one between paper and pencil.
Examples of a coordinate input apparatus are a resistive film input apparatus, an electrostatic input apparatus, an apparatus having a transparent input panel such as an ultrasonic panel for propagating ultrasonic waves on a coordinate input surface made of glass or the like, an optical input apparatus, an apparatus for detecting a position by emitting sound waves into the air, and an apparatus based on an electromagnetic induction (electromagnetic exchange) scheme, which has a coordinate calculating mechanism and transparent protective plate placed on the rear side and front surface of a display, respectively, to form an integral input/output information apparatus.
Such information apparatuses that have recently developed include a pen input computer with a relatively large size or the like along a trend toward larger displays as well as a portable compact electronic notebook. Such information apparatuses are being used for presentation apparatuses, videoconference systems, and the like in combination with large displays such as front projectors, rear projectors, and PDPs. Displays such as large liquid crystal displays and PDP displays have currently been improved in image quality and reduced in cost. In addition, in parallel with digitization of satellite broadcasts and the like, TV specifications/forms have begun to enter an age of transition.
These large displays have replaced, for example, whiteboards or electronic blackboards used in offices and have begun to be used for conferences or meetings in which data prepared in personal computers are displayed on the large displays. In such a case, for example, the contents of information displayed on the display window of a large display can be switched, like those on a whiteboard, by an operator or participant when he/she directly touches the window to control the personal computer so as to update the display information.
Of coordinate input apparatuses of these types, however, a resistive film input apparatus, an electrostatic input apparatus, and the like have difficulty in forming a perfectly transparent input panel, resulting in a deterioration in the quality of images displayed on the display. In addition, in an ultrasonic input apparatus requiring a propagation medium such as a glass member, the surface of the glass member must be optically processed to prevent the glare of a fluorescent lamp when the apparatus is used indoors. It is therefore inevitable that it will cost much to maintain the quality of images. An electromagnetic induction input apparatus has a matrix of electrodes formed on the rear side of the display surface, and transmits/receives electromagnetic signals to/from an input pen. As a display apparatus increases in size and thickness, it becomes difficult in principle to calculate coordinates. In addition, when a large coordinate input apparatus is to be formed based on this technique for conferences or presentation, the apparatus becomes very expensive.
When a large display apparatus is to be used, the apparatus is required to have sufficient performance in terms of viewing angle, contrast, and the like because it is assumed that a large audience will watch the screen. When, therefore, such a large display apparatus and coordinate input apparatus are to be combined, it is a significant challenge to prevent a deterioration in the image quality of the display apparatus as well as allowing high-precision calculation of coordinates at a sufficiently low cost.
Consider a large integral input/output system of this type. In consideration of a meeting with a large number of participants and the network age, the system is preferably designed to allow an inquirer to operate a screen in an arbitrary place by remote control or acquire information from a network, as needed, as well as making an operator control a personal computer by directly touching the screen.